Date of Completion
Gary Robbins, Jean Crespi, Glenn Warner
Field of Study
Master of Science
This study examined the effects of winter deicing on groundwater quality beneath an 860-m2 permeable asphalt parking lot at the University of Connecticut in Storrs, Connecticut. While the beneficial impacts of permeable asphalt on water quality and hydrology have been documented in the literature and include increases in groundwater recharge, reduced peak flows and reductions in metals and hydrocarbon contaminant concentrations in groundwater, chloride has not been observed to be filtered from percolate beneath permeable asphalt. The potential issues related to chloride contamination of groundwater include aquatic toxicity and heavy metals mobilization. Monitoring wells were installed up-gradient and down-gradient in which electrical conductivity was monitored at 10 minute intervals from September 26, 2014 to May 8, 2014. Biweekly samples were collected and analyzed for chloride during the period of study and used to develop a predictive relationship which allowed electrical conductivity to serve as a proxy for continuous chloride concentrations. Samples were also analyzed for sodium (Na), calcium (Ca) and magnesium (Mg) on two occasions before deicing activities began in September and October 2014 and two occasions while deicing activities were active in January and March 2015 and used to evaluate cation exchange potential.
Changes in electrical conductivity and chloride were found to be directly proportional to changes in water table elevations after deicing salt applications and snowmelt percolation and inversely proportional during non-winter months due to dilution by percolating water. Chloride concentrations in groundwater beneath permeable asphalt increased by 9,480 % over the period of study, though the mean concentration of 303.7 mg/L calculated down-gradient was lower than the up-gradient mean concentration of 1,280 mg/L. Ca and Mg in the down-gradient well increased by 4,632% and 1,946%, respectively, though metals concentrations in the up-gradient well were higher than down-gradient for all sampling dates. Despite the frequent high peaks of chloride as well as the increases in metals observed in the down-gradient well, monitoring throughout the study period revealed lower contaminant concentrations down-gradient than up-gradient before and after deicing activities were active. These results suggest that the use of permeable asphalt in environments with high background contaminant concentrations is beneficial to shallow groundwater quality in the long term due to dilution.
Angel, Derek R., "Winter Deicing Effects on Groundwater Quality Beneath Permeable Asphalt" (2015). Master's Theses. 814.